In the prior art, a known linear actuator includes a stator formed by an electromagnet, a movable element provided with a permanent magnet, and a control unit for controlling drive current that is supplied to a coil of the electromagnet. The linear actuator reciprocates and oscillates the movable element relative to the stator (refer to patent document 1). A method for detecting movement (displacement, speed, or acceleration) of the movable element by detecting the induced voltage generated at the coil of the electromagnet has been proposed for the linear actuator.